Method and apparatus for controlling continuous tandem rolling mills

ABSTRACT

In a continuous tandem rolling mill, for varying the gauge of a strip during high speed rolling operation thereof, the number of pulse signals from a pulse transmitter associated with a deflector roller on the entry side of a plurality of mill stands is counted in response to a signal from a gauge varying point detector disposed on the entry side of the mill, the first mill stand is set to a predetermined rolling schedule when the number of pulse signals counted has reached a predetermined value under the assumption that the gauge varying point reaches the first mill stand, at the same time the counting operation of the number of pulses from a pulse transmitter associated with the roll of the first mill stand is commenced, the second mill stand is set to the predetermined rolling schedule when the counted number of pulses from the last mentioned pulse transmitter reaches the predetermined value, and similar setting operations are repeated for succeeding mill stands until the last mill stand is set to the predetermined rolling schedule.

United States Patent 11 1 Fujii et al. Aug. 7, 1973 [54] METHOD AND APPARATUS FOR 3,109,966 11/1963 Buys 317 157 CONTROLLING CONTINUOUS TANDEM 3,603,124 7/1971 Arimura et al. 72/8 ROLLING MILLS I [75] inventors: SeijiFujii; Hiroshi Kuwamoto; jz g igi ggg g y g gfi Mehr Masayuki Ishida, all of Fukuyama; Masamato Kamata, Kawasaki, all f Japan 1 [57] ABSTRACT in a continuous tandem rolling mill, for varying the Asslgneel pp Kflbushiki Kaisha, gauge of a strip during high speed rolling operation Tokyo, Japan thereof, the number of pulse signals from a pulse transmitter associated with a deflector roller on the ent [22] Filed 1971 side of a plurality of mill stands is counted in respon [2i] Appl. No.: 119,220 to a signal from a gauge varying point detector disposed on the entry side of the mill, the first mill stand is set to a redetermined rollin schedule when the number [30] Forelgn Application Priority Data of P1588 signals counted as reached a predetermined Mar. 7,1970 Japan 45/19212 value under the assumption that h gauge varying point reaches the first mill stand, at the same time the [52] US. Cl. 72/12 counting operation of the number of pulses from a [51] [lit- Cl Bzlb 37/14 pulse transmitter associated with the l of the first [58] Fleld of Search 72/7-1 1, in Stand is commenced the second mil] stand i set to 7 240 the predetermined rolling schedule when the counted number of pulses from the last mentioned pulse trans- [56] References and mitter reaches the predetermined value, and similar UNITED STATES PATENTS setting operations are repeated for succeeding mill 3,564,882 2/1971 Harbaugh et al. 72/3 stands until the last mill stand is set to the predeter- STAND NO. I

STAND No.2 2 STAND 110.3

g Quinn No.4

STAND NO. 5

QQQg

mined rolling schedule.

8 Claims, 1 Drawing Figure ROLL DIAMETER (MANUAL SET) SLIP RATE (MANUAL SET) CORRECTION COMPUTER MOTOR SPEED CONTROL FOR ROLL STANDS SCREW DOWN POSITION SETTING FOR ROLL STANDS PATENIED AUS 7 I975 STAND NO. I

STAND NO. 2

STAND NO. 3

CORRECTION COMPUTER STAND NO 4 ROLL DIAMETER FORWARD SLIP RATE (MANUAL SET) (MANUAL SET N01 STAND SCREW DOWN POSITION SETTING FOR ROLL STANDS METHOD AND APPARATUS FOR CONTROLLING CONTINUOUS TANDEM ROLLING MILLS BACKGROUND OF THE INVENTION This invention relates to a method of controlling rolling mills and more particularly to a method and system for controlling a continuous tandem rolling mill capable of varying the rolling schedule during the high speed operation of the mill for producing products of different gauges.

Where it is desired to perform so-called stepped rolling, that is to produce a metal strip having different gauges on one and the other halves of the length of the strip, it has been the practice that after stopping the rolling mill or after decreasing the rolling speed to a very low speed, the operator manually varies the gauge setting. In modern continuous rolling mills, the leading end of a succeeding strip is welded to the trailing end of a preceding strip so as to continuously roll a very long strip. In such a continuous rolling mill system it is necessary to vary the rolling schedule or the gauge of the product during the rolling operation.

To operate the continuous rolling mill at the highest operating efficiency it is essential not to stop the operation of the rolling mill and to operate it at as high a speed as possible. For this reason, where the thickness of the starting strip or the product is to be varied by varying the gauge, it is desirable to vary the gauge while maintaining the speed of the rolling mill at as high a speed as possible.

However, when the gauge is varied under a high rolling speed, even a slight change in the gauge or in the timing of varying the gauge, may cause a large variation in the tension of the strip, thus not only producing a large quantity of off-gauge products but also resulting in the breakage of the strip.

Also, in the stepped rolling operation, it is highly desirable to vary the gauge under a high speed operating condition and under a condition to minimize the variation in the strip tension in orderto improve the rolling efficiency and to decrease the risk of breakage of the strip.

To this end, it is necessary to vary the gauges at respective mill stands at a correct timing.

It is therefore an object of this invention to provide a novel control method and system for a continuous tandem mill in which the gauge of the strip being rolled can be varied while the rolling mill is operating at a high rolling speed without the necessity of reducing the rolling speed or stopping the rolling mill.

Another object of this invention is to provide a novel control method and system for a continuous tandem mill capable of varying the gauge of the strip being rolled without causing undue variation in the strip tension, thus preventing breaking of the strip.

A further object of this invention to provide an improved method and system for readily varying the gauge of a continuously moving strip by one man contr'ol.

SUMMARY OF THE INVENTION According to one aspect of this invention, for use in a tandem rolling mill wherein the gauge of the strip is varied during the rolling operation, there is provided a method comprising the steps of commencing the counting operation of a number of pulse signals from a transmitter associated with a deflector roller on the entry side of a plurality of mill stands in response to a signal from a gauge varying point detector which is disposed on the entry side of said plurality of mill stands to detect the passage of said gauge varying point on said strip being rolled, setting the first mill stand to a predetermined rolling schedule when the number of pulse signals counted has reached a predetermined value under the assumption that said gauge varying point reaches said first mill stand, concurrently commencing the counting operation of the number of pulses from a pulse transmitter associated with the roll of said first mill stand, setting the second mill stand to said predetermined rolling schedule when said counted number of pulses from said last mentioned pulse transmitter reaches a predetermined value and repeating similar setting operations for succeeding mill stands until the last mill stand is set to said predetermined rolling schedule.

According to another aspect of this invention, there is provided a control system of a continuous tandem mill including a plurality of spaced apart mill stands and a deflector roller on the entry side of said mill, said control system comprising a gauge varying point detector disposed to detect a gauge varying point on said strip and for producing a pulse signal, a plurality of pulse counters of a number of equal to the sum of the number of said deflector roller and the number of said mill stands, a plurality of pulse transmitters respectively associated with said deflector roller and the work rolls of said mill stands for applying pulse signals to respective counters, means to supply the output pulse from said gauge varying point detector to one of said counters which receives the output pulse from one of said pulse transmitters which is associated with said deflector roller, means for applying the output of each pre ceding counter to each succeeding counter, a correction computer for presetting a predetermined value of the counted number of the pulse signals in each one of said counters and a schedule set value signal transmitter connected to receive outputs from respective counters for transmitting preset rolling schedules for respective mill stands.

Where a welding seam of the strip is utilized as the gauge varying point, the gauge varying point detector may be a detector which provides a pulse signal in response to the weld seam, whereas if such a point is not a weld seam, the gauge varying point may be preset to correspond to a predetermined length of the strip or a predetermined number of convolutions of the strip unwound from a coil. In the latter case, a signal representing the predetermined length may be produced by a signal transmitter connected to the pay off reel or a deflector roller.

Alternatively, a perforation or a notch, or an optical, magnetic or radioactive marking may be provided at the gauge varying point which is detected by a photoelectric detector, width detector, magnetic detector or radiation detector to produce a signal representing the gauge varying point.

To improve the reliability of the detection, two or more different type detecting systems may be combined. Further, to back-up the automatic system, a manually operated push button may be used.

During the interval between the instant at which a signal is generated by the gauge varying point detector and the instant at which the gauge varying point reaches the first stand, the length of the strip on the entry side of the first mill stand existing between the gauge varying point and the first stand is assumed to pass therethrough and the schedule set value signal transmitter transmits the set value to the first stand for the next rolling speed for the different gauge.

Then by assuming that the length of the strip between the first and second mill stands has passed through the mill and hence the gauge varying point has reached the second stand the schedule set value signal transmitter sends the set value regarding the second mill stand during the rolling schedule for the next gauge.

In the same manner, as the gauge varying point reaches the last mill stand the schedule set value signal transmitter transmits the set value regarding the last mill stand during the rolling schedule for the next gauge.

Running of the gauge varying point from one stand to the next stand can be determined by counting the pulse signals from a pulse transmitter mounted on the shaft of a roll, the number of pulses corresponding to the number of revolutions of the roll shaft which in turn is a function of the strip length between adjacent mill stands. As the number of pulses corresponding to the strip length between adjacent mill stands varies dependent upon the roll diameter and the forward slip, it is necessary to make corrections according to following equation where 1 represents the distance or strip length between adjacent mill stands, R the roll diameter, N the number of pulses generated per one revolution of the roll, f the forward slip and k the number of pulses corresponding to the distance between stands.

BRIEF DESCRIPTION OF THE DRAWING The invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawing in which the single FIGURE shows a diagram, partly in block form, helpful to explain the novel control method.

DESCRIPTION OF THE PREFERRED EMBODIMENT The single FIGURE shows a preferred embodiment of the novel control system as applied to a five stand tandem rolling mill installation.

A gauge varying point detector 1 provides a start pulse signal to a pulse counter PCl in response to the passage of the gauge varying point. Pulse transmitter 9 mounted on a deflector roller 2 on the entry side of the mill stands and pulse transmitters -13 are mounted on the operating shafts of the working rolls of respective mill stands 3 to 7 inclusive to supply pulses to pulse counters PC1, PC2, PCS, PC4 and PCS respectively corresponding to the numbers of revolutions of the deflector roller and the working rolls. A value expressed by k I, N,/ 1rRd calculated, for example, by a correction computer 19 is preset in counter PCl, where 1, represents the distance between gauge varying point detector 1 and the first stand 3, N the number of pulses per one revolution of deflector roller 2 and Rd the diameter of the deflector roller. Preferably, the gauge varying point of the strip is at least one of weld seam between sections of the strips, a perforation, a notch, an optical marking, a magnetic marking or radiation marking. Such perforation, notch or markings are preferably on the edge of the strip.

A value expressed by k 1,, N,,/1rR, (l +f,,) is also preset in each one of counters PCZ to PCS by the correction computer, where In represents the distance be tween adjacent mill stands, Nn the number of pulses per one revolution of the working roll. Rn the diameter thereof and fn the forward slip.

Upon receipt of a respective count commencement command signal, each counter PCl PCS starts to count the pulse signals from its associated pulse transmitter PT, PT,,, respectively, and when the counter counts up a predetermined number of pulses preset by the correction computer, there is provided an output signal. Although counter PCl starts its counting operation in response to the start output pulse from the gauge varying point detector 2, counters PC2, PC3, PC4 and PCS are started by the start outputs from preceding counters, which start outputs'are generated when said preceding counters count up preset numbers of pulses.

There is provided a schedule set value signal transmitter 20 in which are preset schedules of respective mill stands for the next gauge by an independent controlling computer or a manual switch, not shown, and these preset schedules are sent to control apparatus for respective mill stands in response to the outputs from respective counters.

Upon completion of one rolling operation, the settings of the respective counters PCl PCS and the schedule set value signal transmitter 20 are modified for the next gauge.

In this manner, according to this invention, it is possible to vary the gauge of the rolled strip during the high speed operation of a continuous rolling mill without the necessity of stopping or reducing the rolling speed and without the risk of excessive variation in the strip tension, thus increasing the operational efficiency.

Thus, it is not only possible to minimize the variation in the strip tension as well as the breakage of the strip and to decrease off-gauge products, but also to save labor because the gauge can be varied by one man control.

While the invention has been shown and described in terms of a preferred embodiment, it should be understood that many changes and modifications will occur to one skilled in the art without departing the true spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. In a tandem rolling mill wherein gauge of a strip is varied during rolling operation, a method of controlling gauge comprising a steps of commencing counting of pulse signals emitted from a pulse transmitter associated with a deflector roller on the entry side of a plurality of mill stands in response to a signal from a gauge varying point detector which is disposed on the entry side of said plurality of mill stands to detect the passage of said gauge varying point on said strip being rolled, setting a first mill stand to a predetermined rolling schedule when the number of pulse signals counted has reached a predetermined value corresponding to when that said gauge varying point reaches said first mill stand, concurrently commencing counting of pulses from a pulse transmitter associated with a roll of said first mill stand, setting a second mill stand to said predetermined rolling schedule when the counted number of pulse signals from said last mentioned pulse transmitter reaches a predetermined value and repeating similar setting operations for succeeding mill stands until the last mill stand is set to said predetermined rolling schedule.

2. The control method according to claim 1 wherein said predetermined value of said counted number of pulse signal is given by an equation where 1 represents the distance between adjacent mill stands, R the diameter of the mill roll, N the number of pulses generated per one revolution of said mill roll and f the forward slip.

3. The control method according to claim 1 wherein.

said predetermined values are preset in each one of counters respectively associated with said deflector roller and the working rolls of said respective mill stands.

4. The gauge control method according to claim 1 wherein said gauge varying point is at least one of the following a weld seam between sections of said strip, a perforation, a notch, an optical marking, a magnetic marking and radiation marking which are formed on said strip.

5. The control method according to claim 4 wherein said perforation, notch, optical marking, magnetic marking or radiation marking are formed on the edge of said strip.

6. A control system of a continuous tandem rolling mill includinga plurality of spaced apart mill stands and a deflector roller means on the entry side of said mill, said control system comprising a gauge varying point detector disposed to detect a gauge varying point on said strip for producing a pulse signal to commence a counting operation, a plurality of pulse counters of number equal to the number of said mill stands, a plurality of pulse transmitters respectively associated with said deflector roller means and the work rolls of said mill stands except for the last mill stand, one of said pulse counters receiving the output pulses from one of said pulse transmitters which is associated with said deflector roller means and for counting the output pulses from said one pulse transmitter after receipt of the pulse signal from said gauge varying point detector, means for applying the output of each preceding counter to each succeeding counter corresponding to successive mill stands, a correction means for presetting a predetermined value corresponding to the number of pulse signals to be counted in each one of said counters, and a schedule set value signal transmitter connected to receive outputs from respective counters for transmitting preset rolling schedules to respective mill stands responsive to said counters counting to said predetermined values.

7. The control system according to claim 6 wherein said correction means comprises a correction comp uter.

8. The control system according to claim 6 wherein said predetermined value preset by said correction means is given by an equation 1rR(1+ f) where 1 represents the distance between adjacent mill stands, R the diameter of the mill roll, N the number of pulses generated per one revolution of said mill roll and f the forward slip. 

1. In a tandem rolling mill wherein gauge of a strip is varied during rolling operation, a method of controlling gauge comprising a steps of commencing counting of pulse signals emitted from a pulse transmitter associated with a deflector roller on the entry side of a plurality of mill stands in response to a signal from a gauge varying point detector which is disposed on the entry side of said plurality of mill stands to detect the passage of said gauge varying point on said strip being rolled, setting a first mill stand to a predetermined rolling schedule when the number of pulse signals counted has reached a predetermined value corresponding to when that said gauge varying point reaches said first mill stand, concurrently commencing counting of pulses from a pulse transmitter associated with a roll of said first mill stand, setting a second mill stand to said predetermined rolling schedule when the counted number of pulse signals from said last mentioned pulse transmitter reaches a predetermined value and repeating similar setting operations for succeeding mill stands until the last mill stand is set to said predetermined rolling schedule.
 2. The control method according to claim 1 wherein said predetermined value of said counted number of pulse signal is given by an equation k lN/(R (1 + f)) where l represents the distance between adjacent mill stands, R the diameter of the mill roll, N the number of pulses generated per one revolution of said mill rOll and f the forward slip.
 3. The control method according to claim 1 wherein said predetermined values are preset in each one of counters respectively associated with said deflector roller and the working rolls of said respective mill stands.
 4. The gauge control method according to claim 1 wherein said gauge varying point is at least one of the following a weld seam between sections of said strip, a perforation, a notch, an optical marking, a magnetic marking and radiation marking which are formed on said strip.
 5. The control method according to claim 4 wherein said perforation, notch, optical marking, magnetic marking or radiation marking are formed on the edge of said strip.
 6. A control system of a continuous tandem rolling mill including a plurality of spaced apart mill stands and a deflector roller means on the entry side of said mill, said control system comprising a gauge varying point detector disposed to detect a gauge varying point on said strip for producing a pulse signal to commence a counting operation, a plurality of pulse counters of number equal to the number of said mill stands, a plurality of pulse transmitters respectively associated with said deflector roller means and the work rolls of said mill stands except for the last mill stand, one of said pulse counters receiving the output pulses from one of said pulse transmitters which is associated with said deflector roller means and for counting the output pulses from said one pulse transmitter after receipt of the pulse signal from said gauge varying point detector, means for applying the output of each preceding counter to each succeeding counter corresponding to successive mill stands, a correction means for presetting a predetermined value corresponding to the number of pulse signals to be counted in each one of said counters, and a schedule set value signal transmitter connected to receive outputs from respective counters for transmitting preset rolling schedules to respective mill stands responsive to said counters counting to said predetermined values.
 7. The control system according to claim 6 wherein said correction means comprises a correction computer.
 8. The control system according to claim 6 wherein said predetermined value preset by said correction means is given by an equation k lN/ pi R (1 + f) where l represents the distance between adjacent mill stands, R the diameter of the mill roll, N the number of pulses generated per one revolution of said mill roll and f the forward slip. 